Electric phonograph resistance type pickup



Oct. 14, 1947. J. J. ROOT ELECTRIC PHONOGRAPH RESISTANCE TYPE 1 1cm? Filed Aug. 2, 1945 Fla; 5

P1. E- l FiG- E Patented Oct. 14, 1947 -OFFICE nLEo'rmo PHON GRA RESISTANCE TYPE PICKUP .lohn J. Boot, New York, N. Y. 2411.))"licatl'on'August2,, 1945, Serial No. 608,527

invention relates to vibration responsive devices suchas phonograph pick-up elements. One ofthe obiectsof myinvention is to provide such a device which shall be capable of producing' fluctuating currents of high amplitude in response to slight excitation so that the device may be highlysensitive and its output require but little amplification.

Another object of my inventioniisto provide a vibration responsive deyicewhiclrshan oifer considerable manufacturing economies. These considerable economies may baa-realized both in the coat. of tbematerials utilizednandi in the simple method: by: which ..they. can be: assembled.

Other objects. of. my invention. will be apparent from the following des'criptionit being understood that the; above general description of the. objects 02' myinvention are intendettto describe and not to limit it in any manner.

Referring to the drawing:

Fig. 1 is an elevational view illustrating an embodiment of the invention.

Fig. 2 is a section on the line 2--2 of Fig. 1.

Fig. 3 is a sectional view taken on the same plane as Fig. 1.

Fig. 4 is separate view of the armature used in the embodiment illustrated.

Fig. 5 is a schematic view illustrating the electrical equivalent of the device and as disposed in a conventional circuit.

The device comprises a metallic member III of stepped construction formed by the lower block II and the integral upper block l2. The rectangular shape of the device is effected by securing individual blocks l3 and I4 into the staggered opposite rectangular spaces formed by the stepped blocks H and I2. Blocks l3 and M are of electrical insulation material such as Bakelite or any of a variety of plastics. However, any well known insulation material may be employed. The blocks I3 and M are connected to the member ID as by bolts 15.

A central opening I6 is formed in the device, the opening extending into all of the blocks as indicated in the dotted lines of Fig. 1.

A resilient member I! which is adapted to vary its electrical conductivity in response to compression is disposed in the opening l6. Resilient member I! may take the form of a plug which is inserted into the opening I6 and retained by its inherent elasticity.

Member I! is formed of a rubber material in which conductive media such as carbon particles have been dispersed. These discrete particles which may average from 40 to 100 microns in size a Claims. (01. lira-$100.41

may beloaded intothe rubber in a molding proce '65s or incorporatedin a sponge rubber so as tobe capable of considerableresistance variations. Either high or low resistances are obtainable depending upon the concentration 0f=1 the-dispersion. A product having. the foregoing characteristics is manufactured by theUnitedStatesRubber Company'und'er thet-rade-markUskon and is referred tom the industry'as conductive rubber- An armature I8 is embedded centrally ofv the member I! so as to be separated thereby from the blocks II and I2. Armature I8 is formed with a tubular holder IQ- Which is adapted to receive. a needle 20 such as usedin phonographs. Set screw 2| serves to maintain, the needle 20 in holder L9.

Lateral actuation of the armature I8, as by movement of the needle; 20 on a phonograph .rec- 0rd, willvary the, electrical resistance between the armature and both blocks l I and I2 by compress, ing themember IT. This action is illustrated in Fig. 3, the changed position of the armature 18 being shown in dotted lines.

Referring to Fig. 3, it will be observed that whereas the armature is swung or pivoted so that its lower portion moves in a direction opposite from its upper portion, the staggered or stepped disposition of the conductive blocks l I and I2 produces mutually similar compression actions so that the abovementioned opposite movements do not effect a mutual cancellation of the resistance changes. The resistance changes between the armature l8 and the blocks H and I2 respectively, are therefore additive. The term additive is used because the resistance changes are in phase rather than out of phase, although it is understood that the joint effect of the parallel resistances will be to lower the resistance path.

The use of an article such as above described in a conventional amplifier circuit is illustrated in Fig. 5. Blocks II and 12 are shown in their electrically parallel relationship in respect to armature I8. A battery 22 provides the potential source, the resistor 23, coupling condenser 24 and grid resistor 25 serving their usual functions in feeding the signal to the electronic tube 26. Resistor 23 may be selected to approximate the average resistance of member H. The member I! is illustrated as a pair or variable resistances on both sides of the armature l8.

It will be apparent that the invention as above described will feed fluctuating voltages to the vacuum tube 26 in response to the resistance changes in the circuit of battery 22. It will be further noted that the tendency of the pivoted 3 armature to produce cancelling changes is substantially eliminated.

I have shown a preferred embodiment of my invention but it is obvious that numerous changes and omissions may be made without departing from its spirit.

For example, while I have described the resilient member ll as comprising rubber in which conductive particles have been dispersed, variations in conductivity in the manner described may be achieved by coating or spraying ordinary resilient rubber with such conductive material. The stretching of the material by the movable armature would effect resistance changes in the material and would be suitable in the circuit described.

I claim:

1. A device of the character described comprising a metallic support, said support being formed of integral stepped areas and having a central opening formed therein, a resilient member adapted to vary its electrical conductivity upon compression thereof disposed in said opening and a swingable armature embedded in said resilient member and adapted to compress portions of said resilient member against said stepped areas of said support when said armature is actuated whereby the electrical conductivity between said armature and each of said areas is varied additively.

2. A device of the character described comprising a metallic support having an opening formed therein, an upper member integral with said support and a lower member integral with said support and with said upper member, each of said members being respectively located on Opposite sides of said opening, a plug of resilient material in said opening and abutting said members at its upper and lower ends respectively, said plug being of electrically conductive material which is resistance adapted to vary its conductivity in response to compression, and an armature disposed in said plug and adapted to be swung so as to compress said plug against said members, said armature being operative upon actuation to effect simultaneous compression of plug areas against said integral members whereby the respective resistance changes between said armature and members are additive.

3. A vibration responsive device comprising an armature arranged for swinging action so that upper and lower portions thereof move in opposite directions, a resilient member surrounding said armature, said resilient member being adapted to vary its conductivity in response to pressure, and electrically conductive members respectively disposed On opposite sides of said armature and adjacent said upper and lower portions so that the swinging of the armature will cause each of said portions to compress said resilient member against one of said conductive members whereby resistance changes produced between each of said portions and said conductive members are additive.

JOHN J. ROOT.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,042,606 Kotowski June 2, 1936 2,368,003 Courcy Jan. 23, 1945 FOREIGN PATENTS Number Country Date 328,497 Great Britain May 1, 1930 

